(1) Field of the Invention
The present invention relates to a wireless electromagnetic signal waveform generating system and method of use with the system capable of digitally controlled amplitude, phase, frequency and polarization modulation in which power generation efficiency is improved for transmitting electromagnetic signals.
(2) Background of the Invention
The partitioned air interface described in U.S. Pat. No. 8,626,232 to Steinbrecher is a radio frequency continuous wave transmitter with air interface efficiencies greater than ninety percent. The assembly of the transmitter is detailed in the reference in which individual polarized radio frequency (RF) ports are each driven by an independent amplifier. The radiated power from each “Epixel” radio frequency port is combined in a far field to create a transmitted signal; the far field being an electromagnetic field at distances greater than (area)/(wavelength) units from the electromagnetic field-generating aperture air interface.
A radio frequency transmitter is more effective if the primary transmission frequency, which is called the carrier, can be amplitude modulated and/or phase modulated in order to increase a data information rate. A single carrier provides only one bit of information whereas numerous bits of information can be transmitted by modulating the carrier.
A modulated radio frequency transmitter can be even more effective if the efficiency of generating the modulated transmission is significantly higher than is presently achievable. The transmitter will be still further effective if the modulated radio frequency carrier frequency of transmission can be rapidly changed over a wide bandwidth by digital frequency selection processes.
There are numerous modulation types that comprise combinations of amplitude, phase, frequency and polarization. One type of modulation that is used extensively in communications is quadrature amplitude modulation (QAM). Quadrature amplitude modulation comprises symbol sets in which the number of symbols within the set is a power of two, such as 2, 4, 8, 16, . . . 2N. The number of symbols in a QAM set is called the order of the set. A radio frequency transmitter that can switch from one QAM order to another QAM order within a few clock cycles is desirable in applications wherein a communications channel is continuously changing.
In the prior art and in support of the present invention, U.S. Pat. No. 6,466,167 by Steinbrecher, discloses digital signal processing algorithms that are processed to create digital images based on energy segments captured by the partitioned air interface. A method detailed in the patent reference uses an observable signal injected into the signal paths to describe phase alignment across the partitioned air interface; otherwise, known as the Eplane.
The system is also described in which a receive mode captures radio frequency signals incident on the air interface of the antenna. An observable signal containing a low frequency component and a high frequency component is generated and inserted into the signal path associated with each partition or Epixel of an Eplane.
The observable signal passes through the same signal path as the radio frequency energy captured by the associated Epixel and can later be used to establish a phase reference at the phase center of each Epixel for the radio frequency energy captured by that Epixel. In this way, the energy captured by a plurality of Epixels can be reassembled in the digital domain as representative of the radio frequency energy incident on the Eplane.
U.S. Pat. No. 7,250,920 to Steinbrecher, teaches a method for using a partitioned air interface in applications where a radar cross-section of the air interface is a system parameter. As part of the interface system, a surface is provided with a plurality of electrically conductive partition elements. The partition elements form a plurality of comparatively small apertures that are referred to as Epixels. Each Epixel captures a portion of propagating electromagnetic waves.
Each captured time energy portion is coupled to a transmission line to form a signal path that is unique to that Epixel. In the signal process, each signal path passes through an analog-to-digital converter; thereby, forming a plurality of digital signal data streams equal in number to the number of Epixels in the partitioned interface.
U.S. Pat. No. 7,420,522 by Steinbrecher teaches a partitioned air interface and a method for determining properties of the partitioned energy capture areas. The patent reference discloses an energy efficient system for radio frequency signal acquisition that is described as a software defined air interface system. The system utilizes elements that partition the air interface, which is called an Eplane into a plurality of segments called Epixels which are used to capture portions of radio frequency signals that are incident on the air interface.
The portions of the RF signals that are captured by the Epixels are individually processed and are reassembled in the digital domain to create a digital image of the incident radio frequency signal set. When the air interface transmits electromagnetic waves, each Epixel is transmitted independently. The Epixel signals are then collectively combined in the far field to form a radio frequency beam.